add test

Author: KevsterAmp

pandas/tests/series/methods/test_round.py

@@ -72,3 +72,10 @@ def test_round_ea_boolean(self):
         tm.assert_series_equal(result, expected)
         result.iloc[0] = False
         tm.assert_series_equal(ser, expected)
+
+    def test_round_dtype_object(self):
+        ser = Series([0.2], dtype="object")
+        msg = "Expected numeric dtype, got object instead."
+        with pytest.raises(TypeError, match=msg):
+            ser.round()
+